Modeling > Modeling Turbulence > Using Reynolds-Averaged Navier-Stokes Turbulence Models > Troubleshooting
Troubleshooting
Solution of the transported turbulence variables diverge
The residual for any of the transported turbulence variables increases significantly after the startup transient, indicating that the solution of the turbulence field is diverging.
Solution of the transported turbulence variables converges slowly.
The flow residuals are converging well, but the residuals for the transported turbulence variables are not decreasing as fast.
- You can increase the turbulence solver under-relaxation factor if you are confident that the solution is otherwise progressing well, but a value of more than 0.9 is not recommended, since it might result in solution divergence.
Unrealistically high turbulent viscosity impedes flow solution
During the first few iterations, unrealistically high turbulent viscosity values are impeding the flow solution.
- It is possible to make this factor quite small (say 0.01) to cause only a minimal update, but this would typically be done for a few iterations only.
Warnings of limited turbulent viscosity occur
Repeated warnings occur that the turbulent viscosity is being limited in some cells.
- This is both common and acceptable during the first few iterations due to startup transients.
- If the warnings continue to occur as the flow solution nears convergence, it is possible to increase the Maximum Ratio to prevent the warnings.
- Generally one would only increase the Maximum Ratio if the simulation has a very high Reynolds number and no errors seem to be present in the simulation setup.
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